As well known to those skilled in the art, the wind is a phenomenon in which air flows due to its density differences in the atmosphere. The wind has been used since ancient times. These days, as the resources such as petroleum and coal are gradually becoming exhausted, interest toward wind as alternative energy source is increasing.
In this consideration, a windmill is disclosed in the art, which generates electricity using the wind. Referring to FIG. 5, there is shown a perspective view illustrating a conventional windmill. The windmill comprises a support column 4 which is fixedly installed on the ground to have a height of no less than 5 m, a propeller-shaped rotor 6 which is mounted to an upper end of the support column 4 and has at least two blades integrally formed with each other, and a generator 5 which generates electricity using rotation force of the propeller-shaped rotor 6.
In the windmill constructed as mentioned above, as the propeller-shaped rotor 6 is rotated by the wind, the generator 5 generates electricity. Electricity generated by a plurality of windmills operated in this way is collectively charged in a charger to then be appropriately supplied to places under need.
However, the conventional windmill is encountered with a problem in that, only when the wind flows at a velocity greater than a predetermined value and the air has a high density, the propeller-shaped rotor 6 can be rotated to convert the wind into electric power. Therefore, in the case that a gentle wind blows, it is impossible to generate electricity using the conventional windmill. Further, operational efficiency of the windmill is deteriorated in urban areas and mountain villages where the wind direction frequently changes. Moreover, since the conventional windmill is likely to be broken by strong wind, repair and maintenance expenses are increased, whereby economic efficiency is degraded.